1. Technical Field
The present invention relates generally to packet switched infrastructure that supports transmission of video streams; and, more particularly to quality adaptation of video stream transmissions.
2. Related Art
The rapid evolution of the Internet based hardware and software technology has lead to many new applications in recent years. These applications include the delivery of audio and video programming via the Internet to recipient devices in the home, office, and/or public places. Audio and video program transmission include encoding packaging digital audio data and/or digital video data to produce streamed audio and video data, packetizing the encoded audio/video stream using the Internet protocol (or another communication interface standard) and transmitting the data packets to the recipient devices via the Internet backbone, ISPs (the Internet Service Providers), and APs (Access Points), among other devices. Recipient devices typically include personal or laptop computers, televisions, mobile phones, STBs (Set Top Boxes), PDAs (Personal Digital Assistants) and PVRs (Personal Video Recorders), among other devices.
To efficiently use the Internet and device resources such as delivery and storage bandwidth/data transfer consumption, the audio and video streams are compressed during the encoding process prior to being packetized and time stamped. Typical encoding schemes/processes include the MPEG, JPEG, and MP3 families of standards, among others. At a source side (such as the equipment belonging to ISPs who provide these programs), typical operational processes include receiving audio and video programming that is remotely sourced via satellite, fiber optic or the Internet based channels. Other programming may be generated locally, for example, from a local storage device that contains a plurality of DVDs (Digital Video Disks). Then, the audio and/or video programming is encoded, multiplexed, and transmitted to the recipient devices.
The term encoding, in industry, is used very broadly, and the process of such may include one or more of digitization, compression (such as MPEG4 or MP3), time stamping, and packetization. Examples of compression technologies include MPEG4 (for compressing digital video signals), JPEG (for compressing digital pictures), and MP3 (for compressing digital audio signals). Typically, video compression technologies include spatial compression followed by temporal compression. Temporal compression may include the generation of spatially compressed independent frames, followed by the generation of a set of spatially compressed reference (predicted) frames that only carry the difference video information between the independent frame and/or some of the preceding reference frames and current frame and generation of re-referencing (bi-directional predicted) frame that may only carry the difference video information between the independent frame and/or preceding and/or succeeding reference frames and current frame.
At the recipient device, the audio and video packets are decoded and processed as is appropriate. Typically a STB is provided by a satellite or cable program provider to perform decoding and processing. Again, the term decoding may mean several processes to different people, and the process itself may include de-multiplexing, de-packetization, decompression, assembling packets in proper sequential order, digital to analog conversion and then further processing as appropriate to the recipient device. Therefore, at the recipient end, often the processing and buffering capability used to decompress and reassemble the program packets in order becomes a major bottle neck.
Typical problems encountered in delivery of audio and video streams using the Internet Protocol are: (a) limitations in the processing and buffering capability of the recipient devices—such limitations cause problems in the decompression and reassembly of the video stream carrying the programming which results in the recipient device not being able to present programs properly; (b) loss or delay of packets, e.g., IP packets, arriving at the recipient device—this causes the recipient device not to be able to reconstruct video frames in sequential order, for example, resulting in skipping of many frames at a time that may last more than a second; (c) individual loss or delay of video frames in a manner that does not correspond to a loss or delay of corresponding audio data, resulting in a loss of synchronization between audio data; and (d) errors in base video frames, because of spatial compression—an error occurring in a base video frame persists in reference video frames that depend from the base video, causing the error to appear in the video output for a period of time.
These and other limitations and deficiencies associated with the related art may be more fully appreciated by those skilled in the art after comparing such related art with various aspects of the present invention as set forth herein with reference to the figures.